Water monolayers on MgO(100): structural investigations by LEED experiments, tensor LEED dynamical analysis and potential calculations

Water on MgO(100)—An infrared study at ambient temperatures

“…This trend of high heats of adsorption for submonolayer coverages of water on MgO(1 0 0) is consistent with previous experimental data. Gü nster et al in the TPD studies mentioned earlier performed a Redhead analysis on their data and calculated an activation energy of desorption of the water monolayer feature that varies from 62 to 73 kJ/mol depending on the coverage [40], while LEED studies have calculated the heat of condensation for a half a monolayer to be À85.3 kJ/mol for the p(3x2) ice phase on MgO(1 0 0) [38]. For a coverage of half a monolayer of water adsorbed onto the MgO(1 0 0) surface when held in dynamic equilibrium with the vapor phase, we have calculated an enthalpy value of À58 ± 7 kJ/mol.…”

“…The surface interactions that made the low coverage region more energetically favorable have somehow forced those adsorbed molecules into a configuration that make it energetically less favorable for additional water molecules to adsorb onto the adlayer relative to their adsorption (condensation) onto bulk liquid water. Theoretical and experimental studies to ascertain the geometry of the water monolayer on MgO(1 0 0) have determined that the perfect MgO surface accommodates a very stable, flat monolayer with the oxygen atoms of the water molecules adsorbed nearly above the cation sites at 0 K [37,38]. Further theoretical studies show that upon warming to 300 K and at higher coverages a densely packed first layer with water molecules aligned À17°and ± 30°with respect to the surface plane was clearly distinguished from the upper layers exhibiting a more diffuse behavior [31].…”

“…Magnesium oxide cleaved by this method under high vacuum conditions have been shown by both AES and LEED to produce clean (1 0 0) surfaces [38,42]. Magnesium oxide cleaved by this method in a dry nitrogen atmosphere has been shown by XPS to be contaminated with a fraction of a carbon monolayer [43].…”

“…Theoretical studies traditionally indicate that water physisorbs onto the terraces and reacts with defect sites [26][27][28][29][30][31], yet there are a growing number of reports stating that at a critical coverage, the dissociation of water is stabilized by the presence of the lateral interactions of neighboring waters on this surface [32][33][34][35] creating a mixed monolayer of water and hydroxyl groups. The experimental results are equally mixed, with both molecular [36][37][38][39][40] and dissociative [41][42][43][44][45][46][47][48] adsorption being reported. For the most part, the experimental work has been performed in the low temperature/low pressure regime necessary for typical surface analytical techniques.…”

C1s CEBEs of Hydrocarbons on Elemental Oxides. II. The Adsorption Type of CH4 on the MgO Cluster

“…For example, the adsorption of water on MgO (001) surface has been intensively studied experimentally [1][2][3] and theoretically [4][5][6][7][8], in order to determine the conditions that favor physisorption vs chemisorption of molecular water or chemical dissociation.…”